The continuing expansion and world-wide growth of technically sophisticated industries such as those concerned with computers and computer based products including telecommunications equipment have led to concomitant expansion and growth in support industries, particularly those concerned with power supplies. Technically sophisticated computer installations require assured high quality input power supplies not generally available directly from the line outputs of utilities. Accordingly, a wide range of power improvement approaches have been employed by industry. Early efforts to overcome the aberrations of line power supplies evolved a variety of power conditioning devices, for example, uninterruptible power supplies (UPS) using a battery charger, batteries, an inverter, and static switch arrangement which may be installed to evoke waveform re-creation. Further, motor generators have been provided to achieve power assurance. In some approaches, systems have been provided which modify, but do not recreate waveforms, for example, such as voltage regulators or spike suppressors. The latter systems basically are ineffective in the treatment of a variety of adverse conditions which may be encountered. More recently, a polyphase ferroresonant voltage stabilizer or synthesizer has been successfully introduced to the marketplace. In their elementary form, such synthesizers comprise a regulator which is fashioned as a non-linear saturable transformer arrangement in parallel with a capacitor assembly which is supplied from the line source through an input inductor. The saturable transformer components and capacitors form a ferroresonant circuit wherein the reactive components operate beyond the knee of a conventional magnetization curve. Such devices, for example, are described in U.S. Pat. Nos. 4,305,033 and 4,544,877 by Jeffrey M. Powell.
Even more recently, utility interactive systems have been proposed which function to independently generate a sinewave output and which are connected to a utility through some form of inductors. Employing batteries as an independent source, these devices operate with four quadrant inverters and the like in conjunction with a battery second source to skew the phase relationship of the inverter function with the utility line input to develop a selective reactive power flow. These utility interactive systems exhibit excellent power factor characteristics and impose very low distortion on the utility with which they interact.
As the expansion of power supply needs continues, requirements are developing for features of flexibility such that the supplies may be accommodated to a variety of both primary and secondary power sources. For example, as sophisticated electronic installations become located in remote locales, a capability for using any of a variety of alternate energy sources is called for. Power supplies for these applications should be operable not only in conjunction with utility line inputs, but also with such diverse sources as may generate power from wind, water, sun, and auxiliary motors. Further, for a wide variety of applications, power supply corrective systems exhibiting light weight and small size are required. The latter requirements call for a minimzation of the number of line frequency magnetic components, a flexibility of design, and a produceability at practical cost levels.